1 files changed, 74 insertions, 0 deletions
diff --git a/src/crepe/util/OptionalRef.h b/src/crepe/util/OptionalRef.h
new file mode 100644
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--- /dev/null
+++ b/src/crepe/util/OptionalRef.h
@@ -0,0 +1,74 @@
+#pragma once
+
+namespace crepe {
+
+/**
+ * \brief Optional reference utility
+ *
+ * This class doesn't need to know the full definition of \c T to be used.
+ *
+ * \tparam T Value type
+ */
+template <typename T>
+class OptionalRef {
+public:
+	//! Initialize empty (nonexistant) reference
+	OptionalRef() = default;
+	//! Initialize reference with value
+	OptionalRef(T & ref);
+	/**
+	 * \brief Assign new reference
+	 *
+	 * \param ref Reference to assign
+	 *
+	 * \return Reference to this (required for operator)
+	 */
+  OptionalRef<T> & operator=(T & ref);
+	/**
+	 * \brief Check if this reference is not empty
+	 *
+	 * \returns `true` if reference is set, or `false` if it is not
+	 */
+	explicit operator bool() const noexcept;
+
+	/**
+	 * \brief Assign new reference
+	 *
+	 * \param ref Reference to assign
+	 */
+	void set(T &) noexcept;
+	/**
+	 * \brief Retrieve this reference
+	 *
+	 * \returns Internal reference if it is set
+	 *
+	 * \throws std::runtime_error if this function is called while the reference it not set
+	 */
+	T & get() const;
+	/**
+	 * \brief Make this reference empty
+	 */
+	void clear() noexcept;
+
+	//! Copy constructor
+  OptionalRef(const OptionalRef<T> &);
+	//! Move constructor
+  OptionalRef(OptionalRef<T> &&);
+	//! Copy assignment
+  OptionalRef<T> & operator=(const OptionalRef<T> &);
+	//! Move assignment
+  OptionalRef<T> & operator=(OptionalRef<T> &&);
+
+private:
+	/**
+	 * \brief Reference to the value of type \c T
+	 *
+	 * \note This raw pointer is *not* managed, and only used as a reference!
+	 */
+	T * ref = nullptr;
+};
+
+}
+
+#include "OptionalRef.hpp"
+